Fill level measurement devices having fill level radar antennas may be used for detecting the surface topology of a filling material surface of, for example, bulk materials or moving liquids. In such case, the surface of the filling material is frequently scanned using a measuring beam and the surface topology is thus determined. A one-dimensional array, known as a line scanner, composed of a large number of radiator elements, for example, may be used to control the measuring beam, so that the array facilitates a one-dimensional scanning of the filling material surface. If this array is further rotated, a two-dimensional scanning of the surface can take place.